The cautions to be observed in the employment of diaphoretic medicines, as derived from their nature, chiefly respect the determination they produce to the surface; the acceleration of the motion of the blood, which many of them occasion ; the debility which, in conse quence of the discharge, is produced in the system ; and the effects sometimes produced on the vessels of the surface themselves, by the free passage of the blood through them. The conditions of the system, which chiefly require atten tion in their employment, are, the period of infancy ; lax and debilitated habits; constitutions liable to costiveness.
4. Of Diuretics.
These are medicines which, from be ing taken internally, augment the flow of urine from the kidnies, by stimulating its secretion from the mass of circulating fluids. The changes induced in the sys tem from these direct effects, are, a Change in the balance of circulation; a diminution of the quantity of circulating fluids; but more especially of the serosity and of the saline parts of the blood ; an in crease of absorption by the lymphatic ves sels; a diminution of the quantity of mat ter discharged by perspiration ; and an uncommon flow of fluid through the urinary passages.
Diuretics may be divided into such as are stimulant, of which we have instances in squills, broom, colchicum, cantha rides ; refrigerant, as sorrel, berberry, vinegar, cream of tartar ; and diluent, as water, whey, and acidulated waters. Their use and indication may be ascer tained from the following effects: 1. Their producing evacuation ; whence they may be employed to remove superabundant serosity from the blood ; to evacuate morbid accumulations of serum ; to re move morbid acrimony from the blood; to diminish the quantity of circulating fluids, when too great for the state of the system at the time. 2. From their alter ing the mode of circulation; whence they may be employed, to restore the natural secretion of urine, when morbidly dimi nished; to diminish other secretions, when morbidly augmented. 3. From their augmenting the flow of liquid through the urinary passages ; whence they may be employed, to remove ob structions in these passages, and to wash out acrimony from them. These indications may be illustrated by an at tention to the effects of this class of medicines, as employed in ascites, icto rus, and nephritis.
5. Of Cathartics.
These are medicines which, taken in ternally, increase the number of stools, by stimulating the alimentary canal, in creasing the peristaltic motion of the in testines, and promoting the secretion of the fluids which constitute alvine evacuations. They may be subdivided
into the following tribes : stimulant, as jalap, aloes, bitter-apple ; refrigerant, as Glauber's salts, sal polychrest, cream of tartar ; astringent, as rhubarb, rose leaves ; and emollient, as manna, mal lows, castor oil.
The changes induced in the system from the primary effects of cathartics, are, the evacuation of the contents of the intestines; a diminution of the quan tity of circulating fluids, and, in a parti cular of the serosity ; a change in the balance of circulation; a diminu tion of perspiration ; higher excitement of the nervous energy in the system in general, but more especially in the intes tinal canal.
The indications which cathartic medi cines are capable of fulfilling, may be de rived from the three following sources : 1. From their producing evacuation ; whence they may be employed, to obvi ate morbid retention of the contents of the intestines ; to diminish the of circulating fluids when too great for the then state of the system; to evacu ate morbid accumulations of serum. 2. From their altering the balance of circu lation ; whence they may be employed to promote free circulation through the in testines, in those cases where it is mor bidly impeded ; and to diminish the im petus of the blood against parts morbidly affected. 3. From the affection pf the nervous system which they occasion ; whence they may be employed to re move torpor in the muscular fibres of the intestines ; and to restrain inordinate mo tions in their muscular fibres, These in dications may be illustrated and confirm ed, from considering the eflects of this class of medicines, as employed in dysen tery, small-pox, dropsy, obstructed men struation, and diarrhoea.
The cautions to be observed in the em ployment of cathartics, as derived from their nature, chiefly respect the degree of evacuation they produce from the cir culating fluids, and the topical irritation they occasion to the intestines themselves. The conditions of the system which chief ly require attention in their employment, are, childhood, female habits, hysterical constitutions, high degrees both of irrita bility and torpor, remarkable delicacy of the stomach and peculiar antipa thies. The circumstances chiefly to be regarded with respect to the regimen necessary for this class, are, the mode of exhibiting the cathartic ; the time at which it is given ; the temperature in which the patient is kept during its ope ration ; the diet employed ; and the de gree of exercise he uses.